Hard disk drives are common information storage devices. FIG. 1a provides an illustration of a typical disk drive unit 100 essentially consisting of a series of rotatable disks 101 mounted on a spindle motor 102, and a Head Stack Assembly (HSA) 130 which is rotatable about an actuator arm axis 105 for accessing data tracks on disks during seeking. The HSA 130 includes at least one drive arm 104 and HGA 150. Typically, a spindling voice-coil motor (VCM) is provided for controlling the motion of the drive arm 104.
Referring to FIG. 1b, the HGA 150 includes a slider 103 having a reading/writing transducer (not shown) imbedded therein, a suspension 190 to load or suspend the slider 103 thereon. When the disk drive is on, a spindle motor 102 will rotate the disk 101 at a high speed, and the slider 103 will fly above the disk 101 due to the air pressure drawn by the rotated disk 101. The slider 103 moves across the surface of the disk 101 in the radius direction under the control of the VCM. With a different track, the slider 103 can read data from or write data to the disk 101.
FIG. 1c shows a conventional suspension, the suspension 190 includes a load beam 106, a base plate 108, a hinge 107 and a flexure 105, all of which are assembled together.
The load beam 106 is connected to the base plate 108 by the hinge 107. A locating hole 112 is formed on the load beam 106 for aligning the load beam 106 with the flexure 105. And the load beam 106 is welded with the flexure for increasing the strength of the entire structure.
The base plate 108 is used to enhance structure stiffness of the whole HGA 150. A mounting hole 113 is formed on one end of the base plate 108 for mounting the whole HGA 150 to the motor arm 104 (referring to FIG. 1a). Another hole 110 is formed on the other end of the base plate 108, which is aligned with a hole 110′ formed on the hinge 107 and a hole 110″ formed on the flexure 105. The hinge 107 has a mounting hole 113′ formed on its one end corresponding to the mounting hole 113 of the base plate 108, and the hinge 107 is partially mounted to the base plate 108 with the mounting holes 113′, 113 aligned with each other. The hinge 107 and the base plate 108 may be mounted together by laser welding at pinpoints 109 distributed on the hinge 107. Two hinge steps 115 are integrally formed at two sides of the hinge 107 at one end adjacent the mounting hole 113′ for connecting with the flexure 105.
The flexure 105 runs from the hinge 107 to the load beam 106. The flexure 105 has a proximal end 119 adjacent the hinge 107 and a distal end 118 adjacent the load beam 106. A locating hole 112′ is formed on the distal end 118 of the flexure 105 and aligned with the locating hole 112 of the load beam 106, thus obtaining a high assembly precision. A suspension tongue 116 is provided at the distal end of the flexure 105 to carry the slider 103 thereon.
As illustrated in FIG. 1d, the flexure 105 has a leading portion 121 adjacent the suspension tongue 116, and a trailing portion 122 opposite to the leading portion 121. A plurality of electrical traces 120 is formed on the flexure 105 along length direction thereof. More specifically, the electrical traces 120 begin with the leading portion 121 and terminate at the trailing portion 122. The suspension tongue 116 has a plurality of bonding pads 117 formed thereon for coupling the slider 103. One end of the electrical traces 120 connects to the bonding pads 117, and the other end thereof is electrically connected to a signal processing circuit, such as an integrated circuit (not shown). Generally, the electrical traces 120 extending from the bonding pads 117 includes three pairs which respectively are a pair of read traces, a pair of write traces and heat traces. All of traces will be jointed to several terminal pads 126 at the trailing portion 122.
As always, electrostatic discharge (ESD) may be generated any time during the fabrication, assembly, testing and shipment of the disk drive units. Specifically, ESD may be generated during fabrication of the magnetoresistive head, the head gimbal assembly, the E-block assembly, the final disk drive units, electrical testing of component and shipment of the components. In response, various procedures and equipment have been installed to control ESD levels during every stage of handling through final disk drive assembly to prevent damage to the reader element caused by ESD, especially during the head gimbal assembly. That is because the magnetoresistive heads nowadays have much smaller size, which results the reduced ESD threshold, and there is no any integrated circuit (IC) for ESD protection in head gimbal assembly.
Traditional ESD protection structure always needs additional material, for example, using surface mount technology (SMT) bleed resistors between the traces and ground to release the static charge on the traces; or forming an ESD dissipative polyimide (PI) layer between trace and conductive substrate to release the static charge on the traces; or covering a dissipative/conductive polymer layer on the outer surface of the flexure to achieve low charge voltage on the read traces and protect from ESD damage. However, these solutions are complex and need much additional material which leads to a high manufacturing cost.
Thus, there is a need for an improved suspension with ESD protection structure, HGA and disk drive unit that do not suffer from the above-mentioned drawbacks.                References cited:        U.S. 2002/0154454 A1, Oct. 24, 2002, Kupinski et al.;        U.S. 2006/0187587A1, Aug. 24, 2006, Arai et al.;        U.S. Pat. No. 6,801,402 B1, Oct. 5, 2004, Subrahmanyam et al.;        U.S. Pat. No. 7,692,899 B2, Apr. 6, 2010, Arai et al.;        U.S. Pat. No. 8,218,267 B2, Jul. 10, 2012, Arai et al..        